Jim:

I use some left over silicone grease for lab uses like joints and rubber stopcocks. Great on vacuum pumps too and holds down to 10E-03 torr! The stuff I was using is pretty high end stuff. I think if you search at advanced-scientific.com or other suppliers, you can get a small 2 oz tub or something for around $10 or so. Never goes bad. I lubed my metal floor pumps and the ones in both my wife's and my vans and haven't had to touch them in 10 years. Heck, don't even know where my grease is. Alternatively, rubber automotive boot grease. If you change your own ignition wire set, that stuff is similar to lab stuff, but in a smaller tube for just $3 at Kragen/O'Reilly or PepBoys.